Fall Control of a Red Clover Cover Crop

A beautiful stand of red clover can provide as much as 75 kg of nitrogen per hectare (when at 40 cm tall) for next years corn crop. However, if the clover crop is not “killed off” in the fall, then preparing a suitable seedbed to plant next years crop in is often significantly delayed resulting in reduced yields. A review of different strategies to control red clover in the fall are presented below.

Managing options for red clover

Fall plowing is the only effective tillage operation for managing red clover (Figure 1). If your preference is to use less aggressive tillage (e.g. chisel plow – Figure 2) or no-till, then a herbicide burndown is needed. Research conducted by the University of Guelph has consistently shown that the best and most cost effective herbicide for controlling red clover is dicamba (e.g. Banvel II, Oracle, Hawkeye) applied at 600 mL/ha (or 250 mL/ac – refer to Figure 3). The application timing of dicamba in many of these trials has gone into to mid- to late-October. This is also an opportune time to manage perennial weeds (using a glyphosate + dicamba tank-mix). The key is to ensure that the air temperature at application is greater than 10 ºC, and that the nighttime temperature after application stays ideally at 5 ºC or greater.

Figure 1. Control of red clover in the spring following fall tillage with a moldboard plow

Figure 2. Control of red clover in the spring following fall tillage with a chisel plow

Figure 3. Control of red clover in the spring following a fall application of dicamba. Note that glyphosate will have to be tank-mixed with dicamba to remove volunteer cereals.

Figure 4. Control of red clover in the spring following a fall application of dicamba at a reduced rate (125 mL/ac).

Figure 5. Control of red clover in the spring following a fall application of 2,4-D.

Figure 6. Control of red clover in the spring following a fall application of glyphosate + 2,4-D.

Figure 7. Control of red clover in the spring following a fall application of glyphosate alone.

Table 1. Red Clover Control and relative cost of various fall management strategies.

Treatment

Rate/ac

Control*

dicamba

250 mL

99%

glyphosate (540 g/L)

+ dicamba

500 mL

+ 250 mL

99%

fall plough

95%

Amitrol

1670 mL

90%

glyphosate (540 g/L)

+ amitrol

500 mL

+ 1000 mL

90%

glyphosate (540 g/L)

1.34 L

85%

2,4-D Ester (700 g/L)

500 mL

65%

Source: Dr. Peter Sikkema, Dr. Clarence Swanton and Dr. François Tardif
* Control evaluated in April following the fall applications

What About Volunteer Wheat?

Since dicamba won’t control any volunteer wheat (Figure 3), glyphosate will need to be tank-mixed (Figure 8). The lowest labeled rate of a glyphosate 540 g/L concentration (i.e. Roundup Weathermax) that can be tank-mixed with dicamba for the control of volunteer cereals is 0.5 L/ac.

Figure 8. Control of red clover in the spring following a fall application of glyphosate + dicamba.

“Field Crop News” is an archive of information dedicated to the production of over 8.5 million acres of field crops in Ontario and a forum for which producers, researchers and industry personnel can share information and ideas. The crop technology team with the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA), faculty at the University of Guelph and Ontario field crop producers continually work together to find ways to improve field crop production. The key learning and outcomes from these collaborations are captured at “Field Crop News”.